Pyrolysis of Leftover Potato Vines: Wide Screening of Resource Variability and Influence of Milling and Washing Pretreatments

Feedstock variability is a major source of uncertainty in the thermochemical valorization of agricultural biomass, yet it is rarely assessed through large sample sets covering multiple harvest years and cultivation conditions. In this study, the pyrolytic behavior of ten samples of leftover potato vines, grown and harvested in South Italy during the years 2016–2025, is investigated using dynamic thermogravimetric analysis under conditions of kinetic control. The differential curves always show the same qualitative multi-peak rate dynamics, attributable, for successively higher temperatures, to extractives, pectin and hemicellulose, cellulose and starch, lignin, and proteins. However, quantitative differences, which can be described in terms of plant aging (short, medium, long), are remarkable, especially in comparison with wood (percentage variation with reference average parameters between −31 and +114%). Simple washing (hot or acidic water) pretreatments can reduce variability and make the pyrolytic behavior of potato vines quantitatively similar to that of wood (for the most effective acid treatment, percentage variation between −2 and +5%). The milling method (single-stage ball milling or two-stage knife and ball milling) does not affect the conversion characteristics except for temperatures above 580 K in the region associated with lignin and protein decomposition.